This invention relates to improved hydrocarbon fuels and motor lubricants which prevent or reverse the octane requirement increase (ORI) phenomenon conventionally observed during the initial portion of the operating life of spark-ignition internal combustion engines. More particularly, this invention is directed to novel fuel and lubricant compositions containing a minor amount of a finely divided, high surface area, solid acid catalyst having a critically high non-volatile surface acidity, which exhibit the aforementioned favorable effect on ORI in spark-ignition internal combustion engines, when added with the combustion intake charge to such engines.
The octane requirement increase (ORI) effect exhibited by internal combustion engines operated on gasoline-type fuels is well known in the art. This phenomenon, which may be briefly defined as the demand by a new or clean motor for fuels having increasingly higher octane numbers in order to exhibit knock-free operation, has been traditionally associated with the accumulation of deposits in the combustion chamber during initial operation of such engines. Thus, during the initial operation of a new or clean engine, a gradual increase in octane requirement (OR), i.e., the fuel octane number required for knock-free operation, is observed with an increasing build up of combustion chamber deposits until a rather stable or equilibrium OR level is reached which, in turn, seems to correspond to a point in time where the quantity of deposit accumulation on the chamber wall no longer increases but remains relatively constant. This octane requirement increase is common to all types of spark-ignition engines and often reaches a so-called "equilibrium value" between about 5 and 20,000 miles or corresponding hours of operation. The actual equilibrium value of this increase can vary with engine design and even with individual engines of the same design; however, in almost all cases the increase appears to be significant with ORI values ranging from about 2 to 10 or more research octane numbers (RON) being commonly observed in modern engines.
Several theoretical explanations have been advanced relating the combustion chamber deposit build up to ORI in spark-ignition engines. For example, it has been proposed that the deposit accumulation reduces the combustion chamber volume to a sufficient degree to result in an increase in compression ratio and octane requirements of the engine. Further, it has been suggested that the deposits act as a heat insulator which promotes knocking. Another theory is based on the view that the deposits become incandescent at combustion chamber temperatures causing pre-ignition of the fuel and air charge. In earlier studies of this phenomenon, e.g., see U.S. Pat. Nos. 2,937,932 and 3,126,261, it was postulated that ORI was due to a substantial degree to the use of organolead antiknock agents in gasoline since the thermal decomposition products of these organometallic additives appeared to catalyze ignition of carbonaceous fuel and/or lubricant decomposition products at low temperatures thereby increasing surface ignition in an engine; surface ignition tendencies being indicative of ORI in the engine. More recent studies on the octane requirements of modern automobile engines operated on lead-free gasoline seem to refute this latter theory relating ORI to lead antiknock agents in that unleaded fuel appears to, in fact, give equilibrium or stabilized ORI values which are invariably higher and many times considerably higher than corresponding values with leaded fuels. For example, in a recent reported study of the ORI characteristics of the 1974 Ford production engine families (see Niles et al SAE Paper 740451 "Establishment of ORI Characteristics as a Function of Selected Fuels and Engine Families", February, 1975), the Ford Motor Company established in comparative tests that unleaded fuel gave ORI values which were 1 to 2 RON's higher in some engines and 3 to 4 RON's higher in other engines than leaded fuel, with the stabilized ORI ranging from 6.5 to 11 RON's for unleaded fuel in the engine families tested. In this Ford study, the stabilized octane requirement for the engine families tested almost always approached, if not exceeded, an RON value of 100. A similar worsening of the ORI problem with unleaded fuels in today's automobiles is indicated by a Coordinating Research Council paper entitled "Octane Requirement Increase in 1973 Model Cars (Phase II: 1973 CRC Road Rating Program) dated February, 1975. In this study involving 102 U.S. cars of the 1973 model year operated on unleaded fuel, the weighted average ORI for 3 different fuel types ranged from 5.4 to 9.0 RON. The lower value, obtained with primary reference fuel (PRF), is reported to be something like 2 octane numbers higher than the PRF value obtained with unleaded fuel in a similar program in 1970-71. In the Ford study and in the CRC study there are indications that more than 12,000 and very likely about 18,000 miles of engine operation are required to reach the stabilized ORI value in most engines. Thus, since the CRC study includes a number of individual tests terminated at or even before the 12,000 mile point, it is possible that the reported average ORI is somewhat below the actual stabilized or equilibrium value.
The implications of the above-mentioned ORI studies with unleaded gasoline are quite significant. Firstly, in view of the large ORI indicated for automobile engine operation with lead-free fuels, it is apparent that the commercially available unleaded 91 RON gasolines, as specified by current governmental regulations, very likely will not provide adequate antiknock performance over the lifetime of today's internal combustion engine designed to operate on lead-free gasoline. This could lead to substantial owner dissatisfaction with automobile antiknock performance in the current and future automobile model years since existing environmental regulations dictate that only unleaded fuel be used in most of the vehicles being produced, i.e., those equipped with catalytic convertors. Thus, these owners won't have the option previously available to switch to leaded regular gasoline having an average RON in the United States of about 93.5 to compensate for the anticipated large ORI; but rather, will have to stay with the commercially available 91 RON unleaded gasolines. Secondly, it is anticipated that the large ORI indicated for lead-free fuel operation will eventually force the production of unleaded gasolines having octane levels significantly above the 91 RON fuel currently produced. The production of an unleaded basestock that would meet these predicted requirements will be an enormous economic and technical task. For example, to manufacture an unleaded gasoline of even 93 RON, in the volume required for the upcoming automobile market, would require expensive blending components and costly changes in refining processes to build up octane-making capability to its highest level in history. Further, from the standpoint of energy conservation, various studies have shown that, in the absence of technological breakthroughs, the production of a lead-free gasoline of 96 RON or greater will expend more energy than is realized in gas economy by having such a fuel available. Thus, if unleaded fuels of b 96 RON or greater are eventually required, a significant diversion of crude oil and increase of energy consumption can be projected for the refining phase over present levels of utilization.
From the foregoing it is believed apparent that the advent of unleaded gasoline as a fuel source for spark-ignited internal combustion engines could very likely lead to an accentuation of the ORI phenonmenon previously observed with leaded fuels having adverse impact not only on the fuel costs to the consumer but also in the very critical area of energy conservation and self-sufficiency. Consequently, any gasoline composition or method which will eliminate the ORI phenomenon or provide octane requirement reduction (ORR) for both leaded and unleaded fuels in the internal combustion engine would be an exceedingly valuable advance in the art.